1. Field of the Invention
This invention relates to the treatment of aqueous liquids for separation and fractionation of polyphenolic compounds such as the anthocyanins which they may contain. The liquids thus treated can be designated as anthocyanic extracts. These extracts are usually produced from various vegetable substances including in particular fruits and by-products of fruits, the extraction being carried out by contacting with water to which one or a number of extractants are added.
2. Discussion of the Prior Art
In conventional techniques, the aqueous extract containing the anthocyanins is commonly subjected to a treatment involving concentration of anthocyanins which is carried out by evaporation of the water. A treatment of this type entails the need for a temperature rise which is detrimental to the quality of the concentrated extract obtained and especially to its composition. Moreover, since the applications of anthocyanins are mainly to be found in the field of food products in which they are employed in particular as coloring agents, purification of the extract is necessary. This purification is carried out in a conventional manner by adding chemical substances which facilitate the precipitation of impurities or by adsorption of these latter on ion exchange resins. These chemical treatments are liable not only to contaminate the final product but also to degrade or to modify the natural anthocyanins to the same extent as heat treatments.
The aim of the invention is to overcome these disadvantages by means of a novel method of treatment of anthocyanic extracts which makes it possible to carry out both the concentration and the purification of anthocyanins without having recourse to excessive heat build-up and without making use of chemical agents which are foreign to the product. This method has a further advantage in that fractionation of the anthocyanins is also ensured.